Sensitizing dyes from bithiazoles



Patented Dec.- 18, 1951 El-ZD ZSTATES PAT ENT OF F I CE 2,579,432 SENS'ITIZING DYE'S FRGMiBITHIAZbIiE'S ELee 0. Hensley, Binghamton, N. Y., assignor to .Generalnniline 1& Film Corporation, New ,York,

L, a corporation of Delaware Nb brewing, Al l lication'ioctoberi31, 19 5 0, 'S'erial'No. 19352-83 6 Claims. Cl. ZED- 24ml) 1 This invention relates to new symmetrical tetran'uclear dyes of the bithiazole type, which are particularly useful "for sensitizing photographic emu'lsio'ns 'and to "photographic silver halide emulsions containing these dyes.

In the preparation of cyanine sensitizing dyes, several heterocyclic bases having two methyl groups have been used in the form :of their diguaternary salts=to obtain asymmetrical dyestuiis with varying degrees of sensitizing activity and sensitizing ranges. The -di-quaternary dyestufis obtained from the dye salts of these bases have a tendency to difiuse in a gelatin layer. Eyes [of this category are illustrated, for example, in United StatesPatents 1:9 94,170 and 2,108,845. It

v2 It is an object :of the present invention to provide symmetrical tetranuclear photqasensitizing dyestufis containing a '4,4-.bi.thiazole nucleus.

A further object is to provide such dyes which are added to photographic silver halideemuls'ions whereby the sensitivity of the emulsion 1's inwill be noted that the brganic bas'e's with two nuclei bya mono orapolywmethine'chain. These new :dyersalts have properties which are ncitzpossessed by the known -.unsym'metrical :dyes. :For instance, the dyes are :not only :sensitizcrs for both orthochromatic and panchromatic .film emulsions, but are also excellent sensitizers for color film, being .unafiected by the presence of color components and exhibiting the property of non-migrationfrom the layer in which they are incorporated.

eti ne creased.

A still further object isxto provide photo-sensitizing dyestuffs having a :strong sensitizing activity :for .color film emulsions and having a lesser ?tendency to :diffuse in gelatin layers.

Other objects and advantages .of this invention will become apparent by reference to the following specification in which its preferred details and embodiments are described This invention is predicated upon the discovery that 1 mol of a diequaternary 2,2-dimethyl-4,4- bithiazole salt containing two methyl groups in the 2,2-positions can be condensed with two mols of a nitrogenous hetero'cyc'lic dye salt of the type used cyan ine dyes. This discovery is wholly 'n-nexpected and surprising since tir-quaternary cyclammonium salts of the prior art prepared from heterocyclic bases having two methyl groups are only reactive throughnone of these groups, but not through both groups.

The symmetrical tetran-uclear dyestuffs prepared according to the present invention are characterized by the following general formulae:

wherein R is an alkyl or aralkyl group, e.g., methyl, ethyl, propyl, butyl, amyl, etc., benzyl, phenethyl and the like, R1 and R2 are either hydrogen or an alkyl group, e. g., methyl, ethyl, propyl, butyl, and the like, R1 being hydrogen only when 1:. equals 1, X represents an anionic acid radical, e. g., C1, Br, I, C104, SO4CH3, SO4C2H5, SO3CsH4CI-I3, and the like, Z represents the atoms necessary to complete a 5- or 6-membered nitrogenous heterocyclic system of the type usual in cyanine dyes, such as pyridine, lepidine, quinoline, indoline; oxazole, thiazoline, thiazole, thiodiazole, pyrroline, selenazole, selenazoline, oxazoline, benzothiazole, benzoselenazole, benzoxazole, naphthothiazole, perinaphthiazole, naphthoselenazole, and the like, and n represents a positive integer ranging from 1 to 2.

The process of preparing theabove tetranuclear cyanine dyes comprises condensing by gentle heating or boiling, or by heating as on a steam bath or under reflux conditions, one mol of a diquaternary cyclammonium salt of 2,2-dimethy1- 4,4'-bithiazole with two mols of a cyclammonium quaternary cyanine dye intermediate of the type used in the preparation of cyanine dyes inthe presence of an acid binding agent, such as a nitrogenous het'erocyclic base containing a small quantity of a tertiary base which may include a wherein R and X have the same values as above, and are obtained by quaternizing 2,2-dimethyl- 4,4'-bithiazole characterized by the following formula:

HaC C-CHa on HC/ N 'K 4 hydrochloric acid and filtered. Upon neutralization, a brownish solid appeared in the filtrate. This solid was filtered off and recrystallized from methanol and had a melting point of 165 C.

The quaternization of the 2,2-dimethyl-4,4'- bithiazole is efiectuated by fusion with an alkylating agent, e. g., an alkyl or aralkyl halide or by heating the base with an alkylating agent, e. g., alkyl or aralkyl halide in a sealed tube in a water bath under increased pressure in the usual manner. The alkylating agent employed may be methyl or ethyl iodide," dimethyl sulfate, methyl p-toluenesulfonate, phenethyl iodide, and the like.

The cyclammonium salts of the type used or proposedfor theproduction of cyanine dyes, and

' utilized in accordance with the present invention may be any one of those having an appropriate group in the reactive position to the nitrogen atom thereof. As examples of suitable cyclammonium quaternary cyanine dye salt intermediates having a reactive group in the 2-position to the nitrogen atom thereof so as to form a dimonomethine dye, the following may be mentioned: 1

In preparing straight chain di-trimethine cyanine dye salts and branched chain di-trimethine cyanine dye salts, the following cyclammonium The 2,2-dimethyl-4,4bithiazole is prepared 7 in the following manner:

Eight and six-tenths grams (0.1 mol) of butanedione-2,3 (diacetyl) in 35 cc. of carbon disulfide were treated dropwise with stirring, with a solution of 10.6 cc. of bromine in 20 cc. of carbon disulfide at the boiling point of the carbon disul- 0.63 gram of thioacetamide were dissolved in 20- cc. of absolute methanol and warmed for 10 minutes on the steam bath. The mixture (asolid had separated) was poured into 100 cc. of water. The aqueous mixture was made acid with diluted quaternary dye salt intermediates having a reactive group in the p-position ofthe side chain in the 2-position of the nitrogen atom thereof may be employed:

2-(13-acetanilidovinyl) -thiazoline ethiodide V 2-(p-acetanilidovinyl) -benzothiazole ethiodide 2- (fl-acetanilidovinyl) -benzoxazole ethiodide 4 2- (18-ethyl-fi-methylmercaptophenyl) -5-methoxy benzoselenazole ethiodide Z-(B-methylmercapto p methylphenyl) -benzothiazole ethiodide 2- (,B-methylmercapto-fl propylphenyl) -benzothi azole ethiodode.'

In preparing straight chain or branched chain dipentamethine and diheptamethine cyanine dye salts, the following cyclammonium quaternary salts having a reactive group in deltaand zetapositions of the side chain in z-position 0f the nitrogen atom thereof may be employed:

2-(4-acetanilido-L3 butadienyD-pyridine ethiodide 2-(4 acetanilido 1,3 buta'dienyl) -benzoxazole ethiodide 2- (4-ethoxy-1,3 -butadienyl) -pyridine ethiodide 2-(4-anilino-3-methyl 1,3-butadienyl) -pyridine ethiodide 2-(4V-anilino-3-methyl 1,3-butadienyl) -p-naphthoxazole ethiodide 2-(4-anilino-3-ethyl 1,3 butadienyD-a-naphthothiazole ethiodide 2- (6-anilino-1,3,5 hexatrienyD-thiazoline ethiodide 2-(6-anilino 1,3,5 hexatrienyl) -a-naphthothiazole ethiodide Z-(G-anilino 1,3,5 hexatrienyl) -p-naphthothiazole ethiodide 2- (6-anilino 1,3,5-hexatrieny1 a-naphthoselenazole ethiodide 2- (6-anilino 1,3,5-hexatrienyl-p-naphthoselen- -azole ethiodide 6 The purified product hada melting point of 245- 246 C. A methanol solution of the dye showed an absorption maximum at 49''! me. The dye sensitized a silver bromoiodide emulsion from 450 my to 570 m with a sensitivity maximium at 540-111;.

Example II The above 'oycloammonium quaternary dye salt intermediates are well known "to the art and hence the methods for their preparation need not be discussed herein. While the above dye intermediates are disclosed as being in the form of the preferred ethiodide, it is to be understood that they may also be employed in the form of other quaternary salts previously mentioned.

.In the preparation of these newsymmetrical tetranuclear dyestuffs, the 2,2-'dimethy1-4,4'- bithiazole base is converted into the corresponding alkyl or aralkyl quaternary oycloammonium salt in the manner usual with the conversion of other nitrogenous heteroc'ylic bases to the quaternary salt for-inJ 7 As previously pointed out, this may beefiectediby fusion with alkyl or ar'alkyl -halide or by heating the base with an alkyl oi aralkyl halide in a sealed tube'ii'n afvvaterbath under increased pressure. A molecular equiva- Int of the quaternary salt thu obtained is heated withtwo molecular equivalents of the cycloammonium cyanine dye salt intermediate in'the presence of a condensing'agent, such as a heterocyclic nitrogenous base or an alcohol containing a 'smallquantity of a tertiary base at reflux ternperature.

condensing agents employed in the preparation'of the new dyes of the present invention, the following may be advantageously employed: heterocyclic nitrogenous bases such as pyridine,

methylpyridine, dimethylpyridine, ethylpyridine,

ethylmethylpyridine, trimethylpyridine, quinoline and the like, or an alcohol, such as methyl, ethyl, propyl, isoprlopyl, butyl, isobutyl and the like, in the presence of a basic tertiary catalyst, such as trimethylamine, triethylamine, and the like.

'The foll'owing examples describe in detail the methods for accomplishing the aboveobjects, but it to be understood that they are inserted merely for the purpose of illustration and Y 0cm 5E5 hHa 2 1- Fiif ty-five hundredths :gram of 2, 2"-dimethyli l-bithiazole di-(ethyl,p-toluenesulfonate) was dissolved in 10 cc. of methanol with slight warming. To this mixture 8 drops of triethylamine were added. After 2 to 3 minutes, 1. 1 grams of 2-(B-ethyl-13-'nethyl-mercaptovinyl) 5 methoxy-benzoselenazole ethiodide were added and the mixture gently boiled for 10 minutes. After cooling the reaction mixture, 25 cc. of 10% aqueous potassium iodide solution were added with stirring. After standing a short time, the solid was filtered on and washed with ether. The crude dye was digested .in :cc. of an equal mixture of methanol and 'isopropanol. After standing overnight, the dye was filtered off and recrystallized from the methanol.

The yield of the dye obtained was .47 gram with a melting point ofT2'30T232 C. A methanol solution of the dye showed an absorption maximum at 5'71 m h The dye sensitized a silver bromoiodide emulsion from 500 my. to 655 m with a sensitivity maximum at 620 m Example 111 tassium iodide were added. The solid Was filtered "are not to be construed as limiting the scope of 'off and washed with water and then ether. The *the'invention.

Example -I product was purified by ('1) digesting with iso- 21- ropanol, (2) digesting with an equal mixture of methanol and isopropanol, (3) digesting with methanol. The mixture was allowed to 0001 each time before the product was filtered off.

The weight of the final product was 0A5 gram with a melting point of 249-250 C. A methanol solution of the dye showed an absorption maximum at'600 m Thedye sensitized a silver bromoiodide emulsion from 520 "m to 670 m with Example IV 7 r o s CH s 8 la/ acaacao gHs 'sulfonate, and 0.3 gram of 2,2'-dimethyl-4,4'-

bithiazole di-(ethyl p-toluenesulfonate) were warmed gently in a free flame with stirring for 4-5 minutes. Five cc. of methanol were added and the mixture boiled until about half of the methanol had boiled oil". Twenty-five cc. of pyridine and drops of triethylamine were added and the mixture boiled for 5 minutes. After cooling, 100 cc. of a 10% potassium iodide solution were added to the reaction solution with stirring. The mixture was allowed to stand 3 hours, the product filtered off and air dried. The dye was digested with 70 cc. of isopropanol. After cooling, the solid was filtered off, dissolved in 150 cc. of hot methanol, filtered while hot, and the filtrate evaporated to about 70 cc. The addition of about one-half volume of ether caused the dye to separate as a powder.

The yield of the final dye was 0.13 gram having a melting point of 267-269" C. A methanol solution of the dye showed an absorption maximum at 573 m The dye sensitized a silver bromoiodide emulsion from 500 mp to 645 111,, with a sensitivity maximum at 620 m Example V Five-tenths gram of Z-(fl-acetanilidovinyl) -4,5-

benzc-benzothiazole methiodide and 0.3 gram of 2,2 dimethyl 4,4 bithiazole di-(ethyl p-toluenesulfonate) in 10 cc. of pyridine containing 10 drops of triethylamine were stirred at room temperature for 5 minutes and then gently boiled for 5 minutes. After cooling, the reaction mixture was diluted with cc of a 10% aqueous solution of potassium iodide. After an hour, the product was filtered off and washed with water and then ether. The product was digested for 15 minutes with 40 cc. of isopropanol. After cooling, the product was filtered off and redigested twice with 40 cc. portions of methanol.

The yield of the purified dye was 0.3 gram with a melting point of 236-237 C. A methanol solution of the dye showed an absorption maximum at 590 m The dye sensitized a silver bromoiodide emulsion from 510 m l to 680 m l, with a sensitivity maximum at 640 m Example VI S G I 411115 32115 jg J21- Forty-five hundredths gram of 2,2-dimethyl- 4,4-bithiazole di-(ethyl p-toluenesulfonate) and 0.8 gram of z-(p-acetanilidovinyl) -benzothiazole in 25 cc. of n-propanol containing a few drops of triethylamine were heated, at gentle reflux, for 18 minutes. Thesolid that separated on cooling was washed with ether and n-propanol. It was then digested with n-propanol. After cooling, the dye was filtered and dried.

The yield of the final dye was 0.3 gram with a melting point of 230 C. A methanol solution of the dye showed an absorption maximum at 5'77 mi. The dye sensitized a silver bromoiodide emulsion from 500 mp. to 650 m with a sensitivity maximum at 610 m Example VII Eighty-seven hundredths gram of 2-(fi-acetanilidovinyl) benzoxazole ethiodide and 0.6 gram of 2,2'-dimethyl-4,4'-bithiazole di-ethiodide were dissolved in 30 cc. of methanol and warmed on a steam bath for 15 minutes in the presence of 10 drops of triethylamine. Five drops of a 40% aqueous solution of sodium perchlorate were added and the mixture warmed another 15 minutes. After cooling, the crystals were filtered oil and recrystallized from methanol.

The crystallized dye had a melting point of 2'73-274 C. A methanol solution of the dye showed an absorption maximum at 532 m The dye sensitized a silver bromoiodide emulsion from 460 m to 605 m with a sensitivity maximum at 560 m Example VIII One and fifteen hundredths gram of 2-(&- acetanilidobutadienyl)-benzoxazole ethiodide, 0.98 gram of 2,2-dimethyl-4,4'-bithiazole di- (phenoxyethyl p-toluenesulfonate), and 8 drops of triethylamine were stirred for 5 minutes at room temperature in 6 cc. of pyridine. The solution was then gently boiled for 4 minutes. After cooling, the dye was precipitated by adding 2 volumes of a 20% aqueous potassium iodide solution. The product was dissolved in methanol and precipitated by thefladdition of a small amount of water. The dye after being crystallized twice from methanol melted at 193-195" C.

The absorption maximum in methanol is 613 1111.0. The sensitization maximum in a silver iodobromide emulsion is at 665 ms with the sensitivity range extending from 540 m l to 700 m In the preparation of emusions containing these tetranuclear cyanine dyes, the dye maybe dissolved in methyl or ethyl alcohol and the alcoholic solution containing from 5 to 50 milligrams of the dye added to a liter of emulsion. While in general practice, it may not be necessary to add the dye in amounts larger than those 10 wherein R represents a member selected from the class consisting of alkyl and aralkyl groups, R1 and R2 represent a member selected from the class consisting of hydrogen and alkyl groups, n represents a positive integer ranging from 1 to X represents an anionic radical, and Z represents the atoms necessary to complete a member selected from the class consisting of 5- and 6- membered nitrogenous heterocyclic system of the 10 type usual in cyanine dyes.

2. A tetranuclear cyanine dyestufi of the following structure:

S OKs cHc \CH HC/ \CCH $13! (5:11; 2I' 8. A tetranuclear cyanine dyestuif of the following structure:

following formulae:

the dyes are applied to the emulsion during any A tetranuclear cyanine dyestufi of the folstage of its production. However, they are preflowing structure:

erably added to the finished emulsion before 0 S S coating.

This application is a continuation-in-part of H20 C CH=CH CH=C my application Serial No. 67,075, filed December 23, 1948, now abandoned. N

While the present invention has been described A in considerable detail with respect to certain preferred procedures, materials, and uses, it is 5. A tetranuclear cyanine dyestufl of the folto be understood that the new classes of tetralowing structure:

nuclear cyanine dyes and their use as sensitizing S S H- dyes is not limited thereto and numerous variations and modifications may be made, as for C CH=CH GH=O CH example, by condensing the di-quaternary amg monium salt of 2,2'-dimethyl-4,4'-bithiazole with a dialkylaminobenzene in the presence of a S (lhH basic condensing agent, e. g., piperidine, di-styryl dyes are obtained. Accordingly, it is intended that the invention be defined only by the accompanying claims in which it is intended to include all patentable novelty residing therein.

I claim:

1. Tetranuclear dyestufis characterized by a E 6. A tetranuclear cyanine dyestufl of the 01- lowing structure:

formula, selected from the class consisting of the 

1. TETRANUCLEAR DYESTUFFS CHARACTERIZED BY A FORMULA SELECTED FROM THE SAME CONSISTING OF THE FOLLOWING FORMULAE: 